Electric protective device.



UNITED STATES lVILliIS P. HARDY, O

PATENT OFFICE.

F OTTUM WA, IOWA.

ELECTRIC PROTECTIVE DEViCE.

SPE FI N formingpart of Letters Patent N 0. 694,855, dated March 4, 1902- Application filed May 4, 1900. Serial No. 15,462. (No model.)

To (LZZ whom it may concern;

Be it known that I, XVILLIS P. HARDY, a citizen of the United States, residing at Ottumwa, in the county of iVappelo and State of Iowa, have invented a certain new and useful Improvement in Electric Protective Devices, (Case No. 1,) of which the following is a full, clear, concise, and eXact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to electric protective devices, and more particularly to that class of protective devices in which instruments or appaatus in electric circuits are protected from abnormal currents, heat-coils entering into the construction of the protective devices to which my invention particularly relates.

Myinvention has for one of its objects the provision of a protective device of this class which will be very sensitive to abnormal changes in the electrical condition of the circuit, but which will be unaffected by general changes in temperature in the neighborhood of the device. I thus provide a protective device that may be located in any convenient place Without regard to the general tempen ature without the liability of having the device prematurely operated, while at the same time abnormal changes in the circuit condition will affect the operation of the device without regard to surrounding conditions. To this end I preferably employ a heat coil or conductor of sufficiently high specific re sistance. l associate two bodies or portions of suitable substance with the heat-coil, which preferably have the same coefficient of expansion, the heat-coil being directly mechanically united with one of the said portions, a nonheat-conducting medium being preferablyinterposed between the said heat-coil and the remaining portion, these portions being mechanically united, so that when the protective coil is heated a deflection in the said portions will occur, whereby they will be shifted, a suitable change in the circuit conditions being thereby effected. In the preferred embodiment of my invention I employ strips of suitable rubber composition, upon one of which a heat-coil is mounted, these strips be ing preferably mechanicallyunited at their ends and capable of relative longitudinal movement between their ends and preferably fixedly mounted at one end upon a suitable base and free to move at the other end. The free or movable end of the protective device carries a circuit changing or controlling portion. The non-heat-conducting element interposed between the strips serves to prevent the heat from being passed from the heat-coil to the strip that does not directly support the same, so that the strip supporting the heatcoil may expand relatively to the companion strip to effect the desired operation of the device.

My invention has also for a further object the provision of an improved lightning-an rester that may be provided in connection with the heat-coil. To this end I preferably employ a carbon medium interposed between terminal plates included in the arrester-eircuit, this carbon being separated from the terminal plates preferably by means of an earthy substance, as sand, mixed with a suitable binding element, as glue.

I will explain my invention more fully by reference to the accompanying drawings,illustrating the preferred embodiment thereof, in which Figure l is a side elevation of a protector constructed in accordance with my invention, a portion thereof being diagrammatically indicated and a part being broken away more clearly to illustrate the nature of the construction. Fig. 2 is a plan view of the instrument shown in Fig. 1, circuit connections being diagrammatically indicated. Fig. 3 is a sectional view on line 3 3 of Fig. 2. Fig. tis asectional view on line i at of Fig. 2. Fig. 5 is a sectional view on line 5 5 of Fig. 2.

Like parts are indicated by similar characters of reference throughout the different figures.

The apparatus is mounted upon a suitable base a, preferably of slate.

The device illustrated herein is designed particularly for the protection of metallic circuits, for which purpose a duplicated structure is employed. Half of the structure illustrated obviously would serve for the protection of the grounded circuits, and I do not, therefore, wish to limit myself to the particular nature of the circuits to which the device may be applied nor to the particular nature of the instruments in the circuit the device is to protect. Binding-screws b I) serve to include the device in circuit; but the device may otherwise be included in circuit, if desired.

Posts 0 are mounted upon the base a, and project above the same, goosenecks cl being adapted to be anchored within the vertical bores in these posts by means of screws e. The unanchored ends of the goosenecks are preferably flattened and are each interposed between strips f and g, composed, preferably, of suitable rubber compound, these strips being securely anchored to the flattened ends of the eccentrics. The opposite ends of the strips are free to swing between suitable abutments, which are preferably provided. The free ends of each pair of strips f and g are mechanically united, so that any swinging movement of a united pair of strips must be due to the expansion of one with relation to the other. The pair of strips serves to con:

trol the condition of the protected circuit in heating coil or conductor h. This heating..-

coil is of fine wire, isformed in convolutions, and is placed upon the face of the strip or plate g farthest removed from the plate or strip f. By this-arrangement the strip 9 is uniformly and quickly heated upon the flow .of abnormal current through the coil; To secure the coil in place, I preferably provide a wrapping 't' of some non-combustible material, as asbestos, about the coil, which is also interposed'between the strips, whereby the heat from the coil and the strip 9 is prevented from passing to the strip f. To further insure the heat insulation of the stripf from 'the strip g, I preferably interpose an additerminal of said coil being preferably in the form of a contact m, which is carried upon the free end of the strip 9 and preferably immovable with relation thereto., This contact normally engages a contact-spring n, which is preferably movable and flexible, as indicated in Fig. 5, this contact-spring being permanently connected with the line. The engaging portions of the contacts m and n are preferably made of platinum. A second contact 0 is preferably provided upon the free end of the strip f, the contacts m and 0 being preferably in direct electrical connection. The alternate contact-springp, similar in construction to contact-spring it, but preferably a trifle thinner, is provided. In the circuits illustrated the contact-spring p isgrounded. If now an abnormal current is'passed through the heating-coil, the strip g, owing 'to the heat generated in the coil, will expand, and as this heat fails to materially affect thestrip f a warping action will occur and the free ends of the stripsfand g-will be swung in a manner to effect connection between the terminals 0 and 19, preferably prior to disconnection between the terminalsn and 0, so that no arc will be established, the circuit, includ ing the heating-coil, not being broken. Thus a ground is placed upon the line, and the main-line circuit is opened by the separation of the contacts on and n, whereby the instru-' ments in the circuit are protected; but the apparatus of my invention may be efiective where the main-line circuit is 'not' opened. The strips fand g willremain'in position to maintain the ground upon the line as long as the heat-coil is subject to abnormal'cu-rrent. If this abnormal current-should be sufliciently great, the fuse Z will be blown, whereby the ,main-line circuit will be opened, the strips f and g being then free to return to their normal position without removing protection from the circuit. This return is effected by the strip f, which previously was under temated when changes in atmospheric temperature occur.

Plates t and u are preferably provided in permanent electrical connection with the contacts n and 19. An interposed medium o, preferably of carbon, is secured between the metal plates t and a. This carbon is insu-' lated from the plates, preferably by means of sand and glue uniting the particles of. sand together. I have shown two layers to w of this earthy material interposed between the carbon block 0 and the supporting-plates; but I .do not wish to be limited to this number. The separating earthy material does not readily hold particles of carbon thatrnay be removed from the blocko in the operation of the arrester, so that short circuits between the plates 25 and 'Lt are absolutely prevented.

ceases limited to the precise construction herein shown; but,

Having thus described my invention, I claim as new and desire to secure by Letters Patent 1. In a device of the class specified, the combination of two strips possessing substantially the same coefficient of expansion, the said strips being mechanically united so as to form a single rigid structure, and held at one end so that the said rigid structure formed by the strips can swing about said end, of a heating device arranged to subject one of said strips to heat due to an excess current, and a circuit-controlling device arranged at the free end of said rigid structure and adapted tobe actuated by the swinging movement thereof, substantially as set forth.

2. In adevice of the class specified, the combination of two strips possessing substantially the same coefficient of expansion, the said strips being mechanically united so as to form a single rigid structure, and being secured at one end, a heating device for heating one of said strips upon the passage of an excess current, and a circuit-opening device arranged at the free end of said strips and adapted to be actuated by the swinging movement of the rigid structure formed thereby, substantially as set forth.

3. In adevice of the class specified, the combination of two strips possessing substantially the same coefficientof expansion, the said strips being mechanically united so as to form a single rigid struetu re, and being secured at one end, a heating devicefor heating one of said strips upon the passage of an excess current, a circuit-opening device arranged at the free end of said strips and adapted to be actuated by the swinging movement of the rigid structure, and a device for rounding the circuit, the said device being operable by the said rigid structure upon the operation of the circuit-opening device, substantially as set forth.

4. In a device of the class specified, the combination of two strips possessing substantially the same coefficient of expansion, the said strips being mechanically united so as to form a single rigid structure and being secured at one end, a heating device for heating one of said strips upon the passage of an excess current, a circuit-opening device arranged at the free end of said strips and adapted to be actuated by the swinging movement of the rigid structure, and a device for grounding the circuit, the said device being operable by the said rigid structure upon the operation of the circuit-opening device, the operation of the grounding device being begun before the completion of the operation of the circuit-opening device, whereby the circuit is grounded before being completely opened,

5. In a device of the class described,the combination with two stripsf and g possessing substantially the same coefficient of expansion, of a heating-coil carried by one of the said strips, a wrapper surrounding the strip and holding the heating-coil in place, said strips being mechanically united at their ends and free from mechanical engagement between the ends, said strips being anchored at one end and free to moye at the opposite end, and circuit-changing means at the free end of the strips, substantially as described.

6. In adevice ofthe class specified, the combination of two strips having substantially the same coefiicient of expansion, the said strips being mechanically united so as to form a single rigid structure and being secured at one end so as to cause a swinging movement of the strips about such end when one of the same is expanded, a heating device for subjecting one of said strips to heat due to excess current, contacts arranged at the free end of said rigid structure, and a contactpost adapted to make connection with said contacts on the structure, the latter being arranged to normally make connection between its contacts and the post and to separate said contacts when one of said strips is heated by the heating device, substantially as described.

7. In adevice of the class specified, the combination with a pair of strips having substantially the same coefficient of expansion, the said strips being mechanically united so as to form a single rigid structure and being held at one end so that the expansion of one of the strips will cause a swinging movement of the structure about that end, a coil of wire arranged to heat one of said strips upon the passage of an unduly large current, a contact-strip carried at the free end of said rigid structure, contact-posts arranged at the opposite sides or" said contact-strip, one of said posts being connected in circuit and the other having a ground connection, and being arranged so that the contact of the rigid structure normally makes connection with the circuit-contact post and separates therefrom, and makes contact with the ground-contact post upon the heating of the coil of fine wire by the unduly large current in the circuit, substantially as described.

In witness whereof I hereunto subscribe my name this 28th day of April, A. D. 1900.

WILLIS P. HARDY, 

